Production of flat metal sheets



Oct. 13, 1964 R, D. STElGERWALT I 3,

PRODUCTION OF FLAT METAL SHEETS Filed June 29, 1960 A fro me} United States Patent PRODUQTIQN 0F FLAT METAL SI-EETS Robert D. Steigerwalt, Pittsburgh, Pa, assignor to United States Steel Corporation, a corporation of New Iersey Filed Iune 29, 1960, Ser. No. 39,542 1 Claim. (Cl. 2919) This application relates to the production of large metal sheets and more particularly to stretcher levelling large steel sheets.

Metal sheet material formed of steel and the like is conventionally flattened or levelled by roller levelling or stretcher levelling. In the former, the sheet or strip material is run through a series of rollers disposed to bend the material in alternate directions and achieve a flattened condition. This is generally applied to strip material but due to the necessity of using rather small diameter rolls is limited to the width of material that can be handled. Stretcher levelling is the method most generally used for flattening plates and is applicable to the heavier sheet gauges. However, large, lighter sheet gauges, i.e. those having alength/thickness ratio in excess of 3000 cannot be stretcher levelled because stretching produces a wavy outof-flat condition.

Accordingly, it is an object of this invention to provide a method of flattening large, light gauge sheets.

The foregoing and further objects will be apparent from the following specification when read in conjunction with the attached drawing, wherein:

FIGURE 1 is an isometric view of an assembly of sheets to be straightened and cover plates therefor, partially broken away to show the interior of the pack;

FIGURE 2 is a side view showing the combined flattening and stretching operation of my invention; and

FIGURE 3 is a view similar to FIGURE 1 of a modification.

Referring more particularly to the drawings the letter P denotes a sandwich or pack composed of outer or cover plates 2 and inner sheets 4 to be stretcher levelled. Preferably the cover plates have a thickness greater than that of the sheets and preferably at least 5 times that of the sheets. Generally the inner sheets are composed of high yield strength steel and are of large size such as 12 feet or more in length and less than .04" gauge thereby having a length/ thickness ratio in excess of 3000.

In FIGURE 2, the pack P is shown disposed between platens 12 with the ends of the pack extending outwardly therebeyond a sufiicient distance to be gripped by grips 20 of a conventional hydraulically operated stretcher levelling machine.

Due to heat treatment, the sheets of the pack are considerably distorted so that preliminary to the stretching operation, pressure may be applied to the platens by a suitable press to partially straighten the sheets and substantially remove warpage therefrom. The Warpage results in the sheets being longer on one side than the other and such EJ522583 Patented Oct. 13, 1964 distortion is removed by the preliminary pressing to pre vent one side being stretched more than the other in subsequent stretcher levelling. Such pressing may be applied to the sheets individually or to the pack.

After pressing the grips are operated to grip the sheets and the cover plates, and tension applied to the assembly to stretch the sheets and cover plates beyond the yield point of the material. The pressure of the cover plates, which may be augmented by the platens, prevents rippling or furrowing of the sheets during stretching so that a completely flattened condition is obtained. The tension may be applied While the pack or assembly is below, at or above room temperature but below the critical temperature.

In one application of the invention the pack P may be assembled prior to rolling to final gauge. In this form the pack will have side bars B surrounding the inner sheets 4.

The side bars are Welded to the cover plates 2 to form a unitary assembly. Following rolling to produce large size sheets and thereafter heating to develop the required physical properties, the assembly is quite distorted and warped and should be flattened and stretched as described in connection with the foregoing assembly of sheets and cover plates.

While I have shown and described certain specific embodiments of my invention, it will be understood that these embodiments are merely for the purpose of illustration and description and that various other forms may be devised within the scope of my invention as defined in the appended claim.

I claim:

A method of producing large fiat heat-treated light gauge sheets having a length/thickness ratio in excess of 3000 comprising disposing a plurality of said sheets between a pair of cover plates having a thickness at least 5 times the thickness of said sheets, reducing said assembly, heat treating said assembly to develop the desired mechanical properties in said sheets, compressing substantially the whole of said assembly between platens and while maintaining compressive pressure on said platens stretching said assembly sufliciently to exceed the yield point of the sheet material.

References Cited in the file of this patent UNITED STATES PATENTS 662,513 Wood Nov. 27, 1900 865,055 Norton Sept. 3, 1907 1,340,149 Browne May 18, 1920 1,910,648 Stringham May 23, 1933 1,914,614 Paisley June 20, 1933 2,021,328 Rendleman Nov. 19, 1935 2,645,842 Orr July 21, 1953 2,961,028 Bath Nov. 22, 1960 FOREIGN PATENTS 680,056 Great Britain Oct. 1, 1952 

